Cabin Fever (2002)

The college friends Paul, Karen, Bert, Marcy and Jeff rent an isolated cabin in the woods to spend a week together. When they arrive, a man contaminated with a weird disease asks for help to them, but they get in panic and burn the man, who falls in the water reservoir and dies. The whole group, except Karen, makes a pact of drinking only beer along the week without knowing where the dead body is. When Karen drinks tap water and gets the disease, the group begins their journey to hell.